LA THÉORIE DE L ÉVOLUTION DE DARWIN

Charles Darwin"s concept of évolution is one de the most solid theory in science. But what exactly is it?


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The Theory de Evolution par natural an option was life formulated in Charles Darwin"s livre "On auto Origin of Species" published in 1859. In his book, Darwin describes how organisms evolve over generations through the inheritance de physical jaune behavioral traits, ont National geographic explains. The theory beginning with thé premise that within a population, over there is sport in traits, such ont beak shape in one du the Galapagos finches Darwin studied.

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According to the theory, people with caractéristiques that enable them to adapt venir their atmospheres will assist them survive and have more offspring, which will inherit those traits. Individuals with less adaptive traits will certainly less generally survive to passage them on. End time, auto traits that permit species venir survive and reproduce will certainly become more frequent in thé population and the population will change, jaune evolve, according to BioMed Central. Through natural selection, Darwin suggested, genetically abonde species can arise indigenous a typical ancestor.

Darwin walk not savoir the mechanism passant par which caractéristiques were passed on, follow to national Geographic. He did not à savoir about genetics, auto mechanism de which gene encode for bien sur traits and those caractéristiques et caractéristiques are passed from one generation to auto next. Hey also did not savoir about hereditary mutation, i m sorry is thé source de natural variation. Marqué future research by geneticists provided auto mechanism et additional evidence parce que le evolution passant par natural selection


What is herbal selection?

Darwin chose the term "natural selection" to be in comparison with "artificial selection," in which animal breeders select pour particular traits that they deem desirable. In organic selection, it"s thé natural environment, fairly than a human being being, the does thé selecting.

Put simply, the theory of evolution par means of natural choice can be described oui "descent v modification," stated Briana Pobiner, année anthropologist and educator at auto Smithsonian national Museum ns Natural history in Washington, D.C., that specializes in thé study ns human origins. The theory is sometimes described ont "survival de the fittest," cible that characterization have the right to be misleading, Pobiner said. Here, "fitness" refers no to année organism"s strength or athleticism cible rather that ability venir survive et reproduce.


Natural an option can change a species in petit ways, leading to a population to change color or size over the arttaserse of numerous generations, follow to thé Natural history Museum. As soon as this procedure happens over a relatively short period du time et in a species or small group of organisms, scientists appel it "microevolution."



Archaeopteryx, presented here in this illustration, is thought about the sapin bird-like dinosaur nous record, dating à about 150 million years ago during thé Jurassic period. (Image credit: Leonello Calvetti/Getty Images)

But when given enough time et accumulated changes, natural choice can develop entirely new species, a procedure known oui "macroevolution," according to Derek Turner et Joyce C. Havstad in "The Philosophy ns Macroevolution." This long-term process is je vous demande pardon turned dinosaurs right into birds, amphibious mammals (such as année animal called Indohyus) right into whales et a usual ancestor of apes et humans into the people, chimps et gorillas we à savoir today.

Darwin additionally described a form de natural choice that counts on an organism"s success at attracting a friend — a process known as sexual selection, follow to nature Education. The colorful plumage ns peacocks and the antlers ns male deer room both examples du traits that evolved under this belles of selection.

How go whales evolve?

One du the meilleur examples scientists oui of natural selection, is the évolution of whales.By making use of Darwin"s theory ont a guide, and understanding comment natural an option works, biologists identified that the transition du early whales from sol to water emerged in a series ns predictable steps.

The evolution of auto blowhole, parce que le example, might oui started through random genetic alters that led to at least one whale having actually its nose farther back nous its head, according à Phys.org.

The whales with this adapter would ont been meilleur suited to a près de la mer lifestyle, since they would not oui had à completely surface to breathe. Such individuals were more successful et had much more offspring. In later generations, more genetic alters occurred, moving auto nose aside from that back conditions météorologiques the head.

Other corps humain parts du early whales likewise changed. Front legs became flippers. Ago legs disappeared. Their bodies became more streamlined, et they developed tail flukes to better propel themselves with water, follow to the Natural background Museum.

Even despite scientists might predict je vous demande pardon early whales must look like, parce que le a long time castle lacked the fossil evidence to back up your claim. Creationists viewed this absence, not just with regard to whale evolution but more generally, oui proof that évolution didn"t occur, oui pointed out in a scientific American article.



This chiffre shows thé semiaquatic "god du death" whale, called auto Phiomicetus anubis. (Image credit: Illustration de Robert W. Boessenecker)

However, since the early 1990s, scientists oui found proof from paleontology, developmental biology and genetics to appui the idea that whales developed from pays mammals. These exact same lines of evidence soutien the theory ns evolution ont a whole.

In the sapin edition of "On auto Origin du Species," Darwin speculated about how natural choice could raison a land mammal venir turn right into a whale. Oui a hypothetical example, Darwin used North American black bears (Ursus americanus), which were known venir catch insects de swimming in thé water through their mouths open, according to auto Darwin post Project.

"I have the right to see no difficulty in a race de bears gift rendered, par natural selection, much more aquatic in your structure and habits, through larger et larger mouths, till a biology was produced ont monstrous as a whale," hey speculated.

The idea didn"t go over very well v the auditeur or with est différent scientists. Darwin was so embarrassed passant par the ridicule he received that auto swimming-bear passage was eliminated from later editions de the book. Scientists now savoir that Darwin had thé right idea but the dorn animal. Instead of looking at bears, hey should oui been spring at cows et hippopotamuses.

Other theories ns evolution

Darwin wasn"t the first or seul scientist venir develop a theory du evolution. Around thé same time as Darwin, anglais biologist Alfred Russel Wallace independently came up with thé theory du evolution de natural selection, according to the Natural history Museum. But this had précis impact.

"The idée of evolution oui a historical occasion was a hot topic among biologists and geologists prior venir Darwin’s livre because over there was sauce soja much evidence accumulating, marqué I devine biological évolution hadn’t yes, really impinged on people outside du the scholastic bunker," agitation P john D. Lambshead, a retired de manière scientifique research leader in marine biodiversity, ecology, and evolution at auto Natural history Museum, London, told toutes les personnes About background Magazine. "As long oui science knew of no mechanism à explain how évolution happened ce could it is in safely dismissed as a crank idea."

Meanwhile, french biologist Jean-Baptiste Lamarck suggest that an organism might pass nous traits venir its offspring, though cette was wrong around some de the details, follow to thé University de California’s musée of Paleontology.

Like Darwin, Lamarck thought that biology adapted venir their environments et passed nous those adaptations. Hey thought biology did this par changing their behavior and, therefore, your bodies — like année athlete working out and getting buff — and that those changes were passed on to offspring.



Maasai giraffe browses on leaves of a high tree in auto Maasai Mara national Reserve, Kenya. (Image credit: Anup Shah/Getty Images)

For example, Lamarck believed that giraffes initially had much shorter necks cible that, oui trees around them thrived taller, they stretched their necks to reach the tasty leaves et their offspring gradually progressed longer and longer necks. Lamarck also believed that first was somehow driven to evolve through auto generations from facile to more complicated forms, according à Understanding Evolution, an educational source from the University of california Museum of Paleontology.

Though Darwin wasn"t sure ns the mechanism par which caractéristiques et caractéristiques were passed on, cette did not think that evolution necessarily moved toward higher complexity, according to Understanding evolution — rather, he believed the complexity developed through organic selection.

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A Darwinian view of giraffe evolution, according à Quanta Magazine, would be the giraffes had actually natural sports in your neck lengths, and that those with plus long necks were better able à survive and reproduce in atmospheres full du tall trees, soja that subsequent generations had more et more long-necked giraffes.

The henn difference between auto Lamarckian and Darwinian ideas of giraffe évolution is the there"s nothing in thé Darwinian explanation around giraffes stretching their necks and passing on an acquired characteristic.

What is modern-day evolutionary synthesis?

According to Pobiner, Darwin go not sait anything around genetics. "He observed thé pattern du evolution, but he didn"t really know about auto mechanism," she said. That came later, with the discovery of comment genes encode various biological or behavioral traits, et how genes space passed under from parents to offspring. The incorporation of genetics right into Darwin"s theory is known oui "modern evolution synthesis."

The physical et behavioral transforms that make herbal selection possible happen at thé level ns DNA and genes within auto gametes, the sperm or egg cells with which parent pass nous genetic material to their offspring. Such transforms are dubbed mutations. "Mutations room basically thé raw material nous which évolution acts," Pobiner said.

Mutations can be caused de random errors in DNA replication or repair, or de chemical jaune radiation damage, according to nature Education. Usually, mutant are one of two people harmful or neutral, cible in rare instances, a mutant might prove useful to thé organism. If so, ce will become more prevalent in the suivant generation and spread throughout thé population.

In this way, herbal selection instruire the evolutionary process, preserving and adding up thé beneficial mutations et rejecting the mauvais ones. "Mutations space random, but selection for them is not random," Pobiner said.



A molecule of DNA coiled inside a cabinet nucleus. (Image credit: Shutterstock)

But natural choice isn"t the seulement un mechanism de which organisms evolve, elle said. For example, genes can be transferred from une population to autre when biology migrate or immigrate — a procedure known oui gene flow. And the frequency of avec certitude genes have the right to also échanger at random, which is dubbed genetic drift.

The factor Lamarck"s theory of evolution is normally wrong is the acquired attributes don"t affect auto DNA of sperm and eggs. A giraffe"s gametes, parce que le example, aren"t affected passant par whether cette stretches that neck; they simply reflect thé genes auto giraffe inherited from its parents. But oui Quanta reported, some aspects of évolution are Lamarckian.

For example, a swedish study released in 2002 in thé European journaux of human Genetics discovered that the grandchildren of homme who starved ont children during a starvation passed on meilleur cardiovascular health to their grandchildren. Researchers hypothesize that although experience such as food deprivation don"t change the DNA assignment in the gametes, they peut faire result in external correction to DNA that rotate genes "on" or "off."

Such changes, dubbed epigenetic changes, aller not modify thé actual DNA sequence itself. Pour instance, a chemical modification called methylation can influence which genes are turned conditions météorologiques or off. Together epigenetic changes can it is in passed down venir offspring. In this way, a person"s experiences can affect auto DNA he or she surmonter down, analogous to the way Lamarck assumed a giraffe craning that is neck would affect thé neck length de its offspring.

What is the evidence for evolution?

The concept of evolution is one of the best-substantiated theories in thé history du science. Ce is supported by evidence native a large variety ns scientific disciplines, consisting of genetics, which spectacles that different species ont similarities in their DNA.

There is additionally evidence support the concept of évolution in paleontology et geology. This is through thé fossil record, which shows comment that species that exist in thé past are various from those present today, according to Bruce S. Lieberman and Roger L. Kaesler in "Prehistoric Life: Evolution et the Fossil Record" (Wiley, 2010).

There is additionally evidence for Darwin"s theory found in developmental biology. Cette has been uncovered that varieties that seem very different as adults passage through similar stages ns embryological development, saying a shared evolutionary past, according to thé open-access textbook "Concepts ns Biology."

Evidence à la whale evolution from paleontology


Ambulocetus natans swim underwater. (Image credit: Nobumichi Tamura/Stocktrek images via Getty Images)

The vital piece ns evidence was found in 1994, when paleontologists found the fossilized remains ns Ambulocetus natans, which means "swimming-walking whale," according à a 2009 review published in the un journal Evolution: Education and Outreach. That is forelimbs had fingers and small hooves, but its hind feet were enormous relatif to the size. The animal was plainly adapted à la swimming, but it to be also capable of relocating clumsily on land, much like a seal.

When it swam, auto ancient creature moved like année otter, pushing earlier with that is hind feet and undulating that is spine and tail.

Modern whales propel themselves through thé water with an effective beats du their horizon tail flukes, marqué A. Natans toujours had a whip-like tail and had à use its legs to provide most of the propulsive renforcer needed venir move with water.

In recent years, more and more of these transitional species, or "missing links," oui been discovered, lending further appui to Darwin"s theory. Pour example, in 2007, a geologist discovered thé fossil of année extinct aquatic mammal, dubbed Indohyus, the was about auto size of a cat et had hooves and a longue tail.

Scientists think thé animal belonged to a coporation, groupe related to cetaceans such as Ambulocetus natans. This biology is thought about a "missing link" in between artiodactyls — a coporation, groupe of hoofed mammals (even-toed ungulates) that contains hippos, pigs, et cows — and whales, according à the intérieur Science Foundation.

Researchers knew that whales to be related à artiodactyls, cible until auto discovery of this fossil, there were no known artiodactyls that common physical characteristics with whales. After all, hippos, thought to be cetaceans" closest living relatives, are very different from whales. Indohyus, conditions météorologiques the other hand, was an artiodactyl, indicated by the structure of its hooves and ankles, and it additionally had part similarities à whales, in the charpente of that is ears, à la example.

Evidence parce que le whale évolution from genes & developmental biology


The critical shore-dwelling ancestor du modern whales to be Sinonyx, top left, a hyena-like animal. End 60 million years, numerous transitional creates evolved: native top venir bottom, Indohyus, Ambulocetus, Rodhocetus, Basilosaurus, Dorudon, and finally, thé modern humpback whale. (Image credit: NOAA)

Genetic evidence also médias the idea that whales developed from pays mammals et provides information about the précisément branching de the evolutionary tree. Parce que le instance, in 1999, researcher reported in the un journal Proceedings of the National academy of sciences that according à genetic analysis de "jumping gene" sequences, which copy et paste themselves into genomes, hippos were whales" closest living relatives. Antérieur à 1985, researchers assumed pigs were an ext closely related venir whales, cible this 1999 study overturned that idea, ont the associated Press reported.

In 2019, researcher reported in the journaux Science Advances around which genes within thé whale genome were inactivated during the process de the creature"s évolution from land mammals, as Science Friday reported. Thé researchers could parlez that bien sur genes, including one involved in do saliva, had actually been inactivated because there space remnants of them, which the researchers appel genomic fossils, in whale genomes. This suggests that whales evolved from a salivating creature.

There"s likewise evidence du cetacean évolution from developmental biology. Developmental biology illustrates auto fact that pets that are very different as adults re-publishing similarities ont embryos since they room evolutionarily related. Pour example, as embryos, cetaceans started to develop hind limbs, i beg your pardon disappear later on in development, while thé forelimbs remain et develop into flippers, according to the journal Evolution: Education et Outreach. This suggests that cetaceans developed from a four-legged ancestor.

Is the theory of évolution controversial?

Despite thé wealth de evidence from the fossil record, genetics et other fields of science, some personnes still des questions the theory de evolution"s validity. Part politicians and religious leader denounce auto theory, invoking a greater being oui a designer to explain auto complex world of living things, particularly humans.

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School boards conflict whether the theory of évolution should be taught alongside other ideas, such ont intelligent conception or creationism.

Mainstream scientists see no controversy. "A parcelle of people have deep spiritual beliefs et also accept evolution," Pobiner said, adding, "there can be genuine reconciliation."

Evolution is well supported by many examples de changes in various types leading to thé diversity of sapin seen today. "Natural selection, or to put it another way — variation, heredity, and differential fitness — is the core theory du modern biology," john Lambshead explains. "It is to biology what, say quantum mechanics and special relativity are to physics jaune the atomic modèle is to chemistry."

Additional reporting by contributors Alina Bradford, Ashley P. Taylor and Callum McKelvie